Non-aqueous secondary batteries (also simply referred to below as “secondary batteries”) such as lithium ion secondary batteries are small and light, high in energy density, and capable of repeated charging and discharging. Such secondary batteries are therefore used in a wide variety of applications. In recent years, improvements in battery members have been studied to obtain even better performance of non-aqueous secondary batteries.
A secondary battery such as a lithium ion secondary battery generally includes battery members such as electrodes (a positive electrode and a negative electrode) and a separator that isolates the positive and negative electrodes from each another to prevent the electrodes from short-circuiting. An adhesive layer or the like for improving the adhesiveness between battery members may be provided on the surface of the electrodes and/or the separator. Specifically, an adhesive layer-equipped electrode obtained by further forming an adhesive layer on an electrode and an adhesive layer-equipped separator obtained by forming an adhesive layer on a separator are used as battery members.
In the production process of a secondary battery, a battery member produced to be long is typically wound as produced and then stored and transported. However, if a battery member including an adhesive layer, such as an adhesive layer-equipped electrode or an adhesive layer-equipped separator, is stored and transported in a wound state, adjacent battery members may adhere via the adhesive layer. That is, defects and a reduction in productivity may occur due to blocking. Accordingly, a battery member that includes an adhesive layer is required to have the capability of inhibiting blocking during the production process (blocking resistance).
Patent literature (PTL) 1, for example, proposes an adhesive for a lithium ion secondary battery, the adhesive including a particulate polymer that has a glass-transition temperature of at least −60° C. and no higher than 20° C. and a particle diameter D50 of at least 300 nm and not greater than 700 nm, and another particulate polymer that has a glass-transition temperature of at least 60° C. and no higher than 150° C., a predetermined particle diameter, and a predetermined degree of swelling in electrolysis solution. Forming an adhesive layer using the adhesive that includes the aforementioned particulate polymer with a high glass-transition temperature and the aforementioned particulate polymer with a low glass-transition temperature as in PTL 1 improves the blocking resistance of the battery member that includes the formed adhesive layer while also improving the adhesiveness between battery members after immersion in an electrolysis solution.